The invention concerns an apparatus for producing a marking on a substrate, preferably a film, in particular a transfer film, comprising a replication apparatus having a replication surface, and a device for producing radiation, preferably a laser installation, which co-operates with the replication apparatus, by the radiation being directed onto at least one irradiation region of the replication apparatus for producing at least one shaping region, and a counterpressure apparatus, wherein a substrate is arranged between the replication apparatus and the counterpressure apparatus in order to shape the shaping region onto the substrate in a contact region between the replication apparatus and the substrate, and a process for producing a marking on a substrate, preferably a film, in particular a transfer film, wherein energy in the form of radiation, preferably laser radiation, from a device producing radiation is used for producing at least one shaping region on a replication surface of a replication apparatus, and wherein the shaping region of the replication surface is shaped onto the substrate by the replication apparatus contacting the substrate under pressure.
The protection of documents by security features has become a standard in the meantime, in the case for example of credit cards, personal identity cards or banknotes. The forgery-proof character of those features is based on the fact that a high degree of special knowledge and extensive apparatus equipment is necessary for the production thereof. A particularly successful security feature which is difficult to copy is an OVD (optical variable device). Embodiments of that security feature have diffractive or holographic structures which, upon a change in the angle of the incidence of light or the viewing angle during visual checking of the authenticity of the security feature, lead to an optical effect such as for example a color change, a motif change or a combination of the two. The security feature can thus be checked in respect of its authenticity without further technical aids. An essential component part of those security elements is a generally thermoplastic or UV-hardenable layer into which the diffractive or holographic structure is embossed in the form of a surface relief. That layer can be part of a transfer film, in which case the security element is firstly produced and thereafter transferred onto the document to be safeguarded. That layer can also be produced in the form of an additional layer directly on the article to be safeguarded. The operation of transferring the surface relief from a mold onto the thermoplastic layer is effected by using rotating stamping cylinders as are described for example in EP 0 419 773 or stamping punches as are disclosed for example in DE 2 555 214. By virtue of the fine diffractive or holographic structures production of the mold is technically very demanding and also cost-intensive. For producing the molds firstly patterns, also referred to as masters, are produced for example by interfering laser beams and etching processes or by electron beam writing, and they are then generally galvanically shaped.
In the case of the known processes, for an enhanced forgery-proof nature, the endeavour is that the same security feature is not applied to each document, but the security features are adapted to the respective document or the identity of the owner of the document, that is to say they are individualized. In that respect two difficulties arise with the above-mentioned processes:
On the one hand a large number of individualized masters would have to be produced, which is very cost-intensive, and secondly the molds would have to be respectively interchanged in the replication apparatuses, and this would result in very long equipment preparation times.
As alternatives, processes and apparatuses are known which shape only partial regions of a mold in order to produce individualized security features.
CH 594 495 describes a process for stamping a relief pattern in a thermoplastic information carrier, wherein selectively only partial regions of the mold are shaped into the thermoplastic layer. In terms of process engineering, those shaping regions are selected by a procedure whereby either those regions are heated by heating bands through which current flows or only selected shaping regions are pressed onto the substrate by a counterpressure device which has partial regions which are adjustable in respect of height. A high level of local resolution in selection of the shaping regions is not to be expected with that process as heat conduction during the long heating-up and cooling-down phase for the heating bands means that the boundaries of the shaping regions can be only inaccurately defined or the dimensions of the shaping regions are established by the dimensions of the bands or the dimensions of the partial regions which are adjustable in respect of height. That process is consequently limited by virtue of having a low level of local resolution.
EP 0 169 326 describes an apparatus for producing a marking on a substrate and the process corresponding thereto. The apparatus has a replication apparatus in the form of an unheated stamping mold and a pressure plate which is in the form of a counterpressure apparatus. The stamping mold has a replication surface which is structured with microstructures which are to be shaped. The apparatus has a laser arrangement for producing a laser beam which is directed onto the substrate through the counterpressure device. The known process provides that firstly the substrate is pressed onto the pressure plate by the stamping punch. Absorption of the laser beam which is incident on the substrate directly in the stamping region and absorption of the radiation reflected at the replication surface of the stamping punch provide that the substrate is selectively locally heated and raised to a temperature at which it can be permanently deformed. In that way shaping regions can be selected and transferred selectively by positioning of the laser beam. A limitation in that process and apparatus is that the laser beam is guided through the substrate. That means that the process is limited to processing substrates which are transparent for the laser radiation and in addition it is highly sensitive to fluctuations in the absorption properties of the substrate, which can occur for example due to fluctuations in material, in dependence on the batch involved.
The object of the invention is to provide an apparatus and a process which permit the production of individualized markings on a substrate, preferably a film, at a low level of apparatus expenditure.
That object is attained by the apparatus set forth in claim 1 and the process set forth in claim 15.